1. Field of the Invention
The present invention relates to a multi-image display system for displaying on a single display device image data received from multiple image sources, and a display method therefor.
2. Related Background Art
Recently, there has been an increase in the use for presentations of image data that are supplied by notebook computers and that are displayed using large display devices, such as liquid crystal projectors or plasma display devices. There has also been an increase in the number of people attending conferences who save data to their computers for later reference, or who exchange files with other individuals who are present. Furthermore, in the future it can be expected that for video conferencing a system will employ PinP (Picture in Picture) to display, in a portion of a display area on a screen, video images of conference participants at remote locations, or that during a conference digital television transmission will be employed to distribute the contents of information that is presented for simultaneous, real-time display.
Because of the above described situation, a demand exists for image display systems whereby multiple, asynchronously received (inputted) image data sets can be simultaneously displayed. Some image display systems of this type employ a method whereby when image data sets are received (inputted) they are temporarily stored in a frame memory, and thereafter are transferred to the display means when the synchronization of all available (input) image data has been completed.
However, in order for a conventional image display system to simultaneously display multiple, asynchronously received (inputted) image data sets, the system must temporarily store the image data, and must delay their transfer to the display means until the synchronization of all image data has been accomplished. Therefore, if the resolution of the received image data is high, and if the data storage capacity is large or the data transfer rate is high, the speed at which the received data is transferred to a frame memory for storage may exceed the data transfer rate for the frame memory. It can be readily seen that this phenomenon will occur more frequently as the number of input sources is increased. And in addition, the above phenomenon will also occur more frequently when multiple, asynchronously received image data sets are simultaneously displayed in a video conferencing environment wherein there are frequent operating condition changes; for example, the sudden addition of an input connection, the alteration of the positions and sizes of multiple display windows, or the sudden shifting to a power saving mode of a computer that is acting as an input source. When a conventional image display system is employed in a video conferencing environment in which the above phenomenon is frequently encountered, display data are abandoned or erased, and the system hangs, so that the degree of freedom provided by the system configuration is lost.
It is, therefore, one objective of the present invention to provide a multiple images display system, for simultaneously displaying multiple image data sets while coping with changes in a display state that are caused by external actions, and a multiple image display method.
To achieve the above objective, according to an aspect of the present invention, a display apparatus comprises:
storage means, for storing image data input by a plurality of input means;
display means, for displaying image data that are read from the storage means;
comparison means, for comparing the sum of the input data transmission rates for the plurality of input means with the data transmission rate for the storage means;
storage control means, for, based on the results of the comparison, inhibiting the storage in the storage means of the image data input by the plurality of input means; and
display control means, for indicating the input means that is inhibited from storing the image data in the storage means.
Furthermore, according to another aspect of the present invention, an image data storage control method, which is applied for a display apparatus that stores, in storage means, image data input by a plurality of input means and that displays, on display means, image data that are read from the storage means, comprises:
a comparison step of comparing the sum of the input data transmission rates for the plurality of input means with the data transmission rate for the storage means;
a storage control step of, based on the results of the comparison, inhibiting the storage in the storage means of the image data input by the plurality of input means; and
a display control step of indicating the input means that is inhibited from storing the image data in the storage means.
According to another aspect of the present invention, a multiple images display system comprises:
a plurality of image data input means, for inputting image data from a plurality of image sources;
a display device, for simultaneously displaying all of the image data that are inputted by the plurality of image data input means;
external action input means, for receiving an external action;
a frame memory, for storing, as frames, the image data inputted by the plurality of image data input means;
transfer means, for reading the image data from the frame memory and for transferring the image data to the display device;
detection means, for detecting the sum of the input data transmission rates for the image data that are inputted by the plurality of image data input means;
comparison means, for comparing the sum obtained for the input data transmission rates with a data transmission rate for the frame memory;
priority allocation means, for determining and allocating display priorities for the image data sets to be displayed on the display device in accordance with the external action; and
control means, for controlling the display, on the display device, of the inputted image data sets in accordance with the display priorities and the result obtained by the comparison of the data transmission rate for the frame memory with the sum detected for the input data transmission rates.
According to another aspect of the present invention, a multiple image display method for inputting image data from a plurality of image sources and for simultaneously displaying, on a display device, all the image data that are inputted, comprises:
an external action input step of inputting an external action;
a storage step of storing in a frame memory, as frames, the image data inputted from the plurality of input sources;
a detection step of detecting the sum of the input data transmission rates for the image data;
a transfer step of reading the image data from the frame memory and of transferring the image data to the display device;
a comparison step of comparing the sum obtained for the input data transmission rates with the data transmission rate for the frame memory;
a priority allocation step of determining and allocating display priorities for the image data sets to be displayed on the display device in accordance with the external action; and
a control step of controlling the display, on the display device, of the inputted image data sets in accordance with the display priorities and the result of the comparison of the data transmission rate for the frame memory with the sum detected for the input data transmission rates.